NSString保留计数-1 [英] NSString retain count -1

问题描述

我想在 didFinishLaunchingWithOptions中的 AppDelegate 类中打印 NSString 的保留计数方法

I want to print retain count of NSString in AppDelegate class in didFinishLaunchingWithOptions method

NSString *str = [[NSString alloc] init];
NSLog(@"str retain count %d",[str retainCount]);

但它总是给-1而不是+1 ....为什么???

but it always gives -1 instead of +1....why ???

推荐答案

NSUIntegerMax 表示返回的对象是不朽的。这曾经在文档中，但后来被删除了（因为非常不鼓励 -retainCount ）。

NSUIntegerMax means the returned object is immortal. This used to be in the docs, but has since been removed (because -retainCount is very discouraged).

在MRC中，有些人实际上会覆盖 -retainCount 以防止他们的单身人士被解除分配。

In MRC, some people would actually override -retainCount to prevent their singletons from ever being deallocated.

在这种情况下，它是 [[NSString alloc] init] 的逻辑优化，用于返回常量/不朽，而不是为每个请求创建一个空字符串。当然，您不应该依赖程序中的这些细节/行为。

In this case, it is a logical optimization for [[NSString alloc] init] to return a constant/immortal, rather than creating an empty string for each request. Of course, you should not rely on this detail/behavior in your program.

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